Day: February 8, 2018

Spring is coming to the northern hemisphere, and soon it’ll be nice enough outside to tool around town on your bicycle. But bikes don’t have power outlets, so phone charging on the go will require forethought and charged-up battery packs. It doesn’t have to be that way. You’re working to make the bike move, so why not make the bike work for you?

If you’ve ever used a motor as a generator, then you can see where this is going. That’s the underlying principle behind [Creativity Buzz]’s bike-powered phone charger. As the bike wheel turns, the rim comes in contact with a small wheel attached to the output shaft of a DC motor. Cranking the output shaft of a motor with permanent magnets inside will induce a small voltage, and here it is amplified with a DC-DC boost converter and output to a USB jack.

As long as you can find a way to secure the phone to the bike frame, or use a long cord and good cable management, you’re in business. Wheelie past the break to watch [Creativity Buzz] build it and give it a stationary test run. While you wait for bike-riding weather, you can still use this kind of charger by turning a crank.

Websites used to be uglier than they are now. Sure, you can still find a few disasters, but back in the early days of the Web you’d have found blinking banners, spinning text, music backgrounds, and bizarre navigation themes. Practices evolve, and now there’s much less variation between professionally-designed sites.

In a mirror of the world of hypertext, the same thing is going to happen with voice user interfaces (or VUIs). As products like Google Home and Amazon Echo get more users, developing VUIs will become a big deal. We are also starting to see hacker projects that use VUIs either by leveraging the big guys, using local code on a Raspberry Pi, or even using dedicated speech hardware. So what are the best practices for a VUI? [Frederik Goossens] shares his thoughts on the subject in a recent post.

Truthfully, a lot of the design process [Frederik] suggests mimics conventional user interface design in defining the use case and mapping out the flow. However, there are some unique issues surrounding usable voice interactions.

Continuous self-affirmation is a vital component to the modern lifestyle. Of course you know the world loves you, but exactly how much do they love you? Checking your phone every few minutes to see if you’ve gained any followers is gauche, and perhaps more to the point, doesn’t let you show off when you’ve got visitors over. In the modern era, the up-and-coming social media star needs a stylish way to display just how popular they are for the world to see.

The counter is powered by a NodeMCU, but you could drop in your favorite variant of the ESP8266 and things would work more or less the same. For the displays, [Becky] is using four Adafruit 7-Segment LED modules, which are easily controlled via I2C which keeps the wiring to a minimum.

It’s interesting to note that since her follower count on Twitter has already hit five digits, two of the display modules are used next to each other for that particular service. Her Instructables and Instagram counters only have one display each however, limiting her counts on those services to 9,999 each. There’s probably something to be learned here in terms of the relative follower counts you can expect on the different social networks if you’re targeting your content to the hacker and maker crowd, but we’ll leave the analysis to those with a better handle on such matters.

Hardware aside, [Becky] spends a lot of time in the video talking about the code she’s come up with to pull her stats from the various services and push them out to the LED displays at a regular interval. It’s nice to see so much attention and explanation given to the software side of a project like this, as more often than not you’re left to your own to figure out what the source code is doing.

Let’s face it: cutting foam with a knife, even a serrated plastic knife meant for the job, is a messy pain in the ass. This is as true for insulation board as it is for the ubiquitous expanded polystyrene kind of foam used for everything from coffee cups to packaging material.

Those stick-type hot wire cutters from the craft store that plug into the wall aren’t much better than a knife. The actual cleaving of foam is easier, but dragging a long, hot flexible wand through rigid foam just right, without making burn marks, is pretty frustrating. It’s not like you can hold the other end to keep it steady. A foam cutter built like a coping saw but held parallel to the wire would offer much better control.

[Techgenie]’s handheld hot wire foam cutter is a simple build based on a single 18650 and a piece of nichrome wire. While this is probably not the most Earth-shattering hack you’ll see today, it’s a useful tool that can be made in minutes with items on hand. Laptop chargers are full of 18650s, and nichrome wire can be sourced from old toasters, hair dryers, or space heaters.

You shouldn’t use just any old wire for this, though, or the battery will get hot and potentially explode. Nichrome wire has a high resistance, and that’s exactly what you want in a tool that essentially shorts a battery to make heat. [Techgenie] used a momentary button instead of a switch, which is a good way to stay safe while using it. It wouldn’t hurt to add some protection circuitry and take the battery out when you’re done. Burn past the break to watch him build it and cut a few tight turns with ease.

Large format photography gives a special quality to the images it produces, due to the differences in depth of field and resolution between it and its more modern handheld equivalents. Projecting an image the size of a dinner plate rather than a postage stamp has a few drawbacks though when it comes to digital photography, sensor manufacturersdo not manufacture consumer products at that size.

[Zev Hoover] has created a large format digital camera, and is using it not only for still images but for video. And it’s an interesting device, for the way he’s translated a huge large-format image into a relatively small sensor in a modern SLR. He’s projecting the image from the large-format lens and bellows onto a screen made from an artist’s palette, a conveniently available piece of bright white plastic, and capturing that image with his SLR mounted beneath the large-format lens assembly. This would normally cause a perspective distortion, but to correct that he’s mounted his SLR lens at an offset.

He does point out that since less light reaches the camera there is also a change in the ISO setting on the camera, but once that has been taken into account it performs satisfactorily. The result is a camera that allows something rather unusual, for Victorian-style large-format images to come to life as video. He demonstrates it in the video below, complete with friends in suitably old-fashioned looking steampunk attire.

Current. Too little of it, and you can’t get where you’re going, too much and your hardware’s on fire. In many projects, it’s desirable to know just how much current is being drawn, and even more desirable to limit it to avoid catastrophic destruction. The humble current shunt is an excellent way to do just that.

Ohm’s Law.

To understand current, it’s important to understand Ohm’s Law, which defines the relationship between current, voltage, and resistance. If we know two out of the three, we can calculate the unknown. This is the underlying principle behind the current shunt. A current flows through a resistor, and the voltage drop across the resistor is measured. If the resistance also is known, the current can be calculated with the equation I=V/R.

This simple fact can be used to great effect. As an example, consider a microcontroller used to control a DC motor with a transistor controlled by a PWM output. A known resistance is placed inline with the motor and, the voltage drop across it measured with the onboard analog-to-digital converter. With a few lines of code, it’s simple for the microcontroller to calculate the current flowing to the motor. Armed with this knowledge, code can be crafted to limit the motor current draw for such purposes as avoiding overheating the motor, or to protect the drive transistors from failure.

In fact, such strategies can be used in a wide variety of applications. In microcontroller projects you can measure as many currents as you have spare ADC channels and time. Whether you’re driving high power LEDs or trying to build protection into a power supply, current shunts are key to doing this.

In parts of the world where it snows a lot and there are requirements for homeowners to keep sidewalks clear, a personal snowblower is it seems an essential piece of equipment. They have traditionally used internal combustion engines, but electric models are also available.

[Joel Clemens] is not impressed by the commercial electric blowers available to him as an American, because their 120 V mains supply just can’t deliver the power to make an effective two-stage design. So he’s built his own using a formerly gasoline-powered blower from a garage sale, and a 240 V industrial motor.

The blower is an impressive piece of equipment even if his running it close to its own cord does look rather hazardous. But the video is also of interest for its examination of the state of access to 240 V outlets for Americans. [Joel] has one for his electric vehicles, and has made a splitter box to give him the required American-style 240 V industrial connector. He makes the point that this is becoming more common as the take-up of electric vehicles gathers pace.